<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>

    let arr = [2,6,1,7,4,]
    let sun = 0
    // 遍历数组
    for (let i = 0; i < arr.length; i++){
      sun = sun + arr[i]
    }
    alert(`${sun}`)
  </script>
</body>
</html>